/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.servlet.mvc.method.annotation;

import java.io.IOException;
import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Locale;
import java.util.Set;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.core.MethodParameter;
import org.springframework.core.ParameterizedTypeReference;
import org.springframework.core.ResolvableType;
import org.springframework.core.io.Resource;
import org.springframework.core.io.support.ResourceRegion;
import org.springframework.http.HttpEntity;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpOutputMessage;
import org.springframework.http.HttpRange;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.converter.GenericHttpMessageConverter;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.http.converter.HttpMessageNotWritableException;
import org.springframework.http.server.ServletServerHttpRequest;
import org.springframework.http.server.ServletServerHttpResponse;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.CollectionUtils;
import org.springframework.util.StringUtils;
import org.springframework.web.HttpMediaTypeNotAcceptableException;
import org.springframework.web.accept.ContentNegotiationManager;
import org.springframework.web.accept.PathExtensionContentNegotiationStrategy;
import org.springframework.web.context.request.NativeWebRequest;
import org.springframework.web.context.request.ServletWebRequest;
import org.springframework.web.method.support.HandlerMethodReturnValueHandler;
import org.springframework.web.servlet.HandlerMapping;
import org.springframework.web.util.UrlPathHelper;

/**
 * Extends {@link AbstractMessageConverterMethodArgumentResolver} with the ability to handle
 * method return values by writing to the response with {@link HttpMessageConverter}s.
 *
 * @author Arjen Poutsma
 * @author Rossen Stoyanchev
 * @since 3.1
 */
public abstract class AbstractMessageConverterMethodProcessor extends AbstractMessageConverterMethodArgumentResolver
        implements HandlerMethodReturnValueHandler {

    /* Extensions associated with the built-in message converters */
    private static final Set<String> WHITELISTED_EXTENSIONS = new HashSet<>(Arrays.asList(
            "txt", "text", "yml", "properties", "csv",
            "json", "xml", "atom", "rss",
            "png", "jpe", "jpeg", "jpg", "gif", "wbmp", "bmp"));

    private static final Set<String> WHITELISTED_MEDIA_BASE_TYPES = new HashSet<>(
            Arrays.asList("audio", "image", "video"));

    private static final MediaType MEDIA_TYPE_APPLICATION = new MediaType("application");

    private static final Type RESOURCE_REGION_LIST_TYPE =
            new ParameterizedTypeReference<List<ResourceRegion>>() {
            }.getType();


    private static final UrlPathHelper decodingUrlPathHelper = new UrlPathHelper();

    private static final UrlPathHelper rawUrlPathHelper = new UrlPathHelper();

    static {
        rawUrlPathHelper.setRemoveSemicolonContent(false);
        rawUrlPathHelper.setUrlDecode(false);
    }


    private final ContentNegotiationManager contentNegotiationManager;

    private final PathExtensionContentNegotiationStrategy pathStrategy;

    private final Set<String> safeExtensions = new HashSet<>();


    /**
     * Constructor with list of converters only.
     */
    protected AbstractMessageConverterMethodProcessor(List<HttpMessageConverter<?>> converters) {
        this(converters, null, null);
    }

    /**
     * Constructor with list of converters and ContentNegotiationManager.
     */
    protected AbstractMessageConverterMethodProcessor(List<HttpMessageConverter<?>> converters,
                                                      @Nullable ContentNegotiationManager contentNegotiationManager) {

        this(converters, contentNegotiationManager, null);
    }

    /**
     * Constructor with list of converters and ContentNegotiationManager as well
     * as request/response body advice instances.
     */
    protected AbstractMessageConverterMethodProcessor(List<HttpMessageConverter<?>> converters,
                                                      @Nullable ContentNegotiationManager manager, @Nullable List<Object> requestResponseBodyAdvice) {

        super(converters, requestResponseBodyAdvice);

        this.contentNegotiationManager = (manager != null ? manager : new ContentNegotiationManager());
        this.pathStrategy = initPathStrategy(this.contentNegotiationManager);
        this.safeExtensions.addAll(this.contentNegotiationManager.getAllFileExtensions());
        this.safeExtensions.addAll(WHITELISTED_EXTENSIONS);
    }

    private static PathExtensionContentNegotiationStrategy initPathStrategy(ContentNegotiationManager manager) {
        Class<PathExtensionContentNegotiationStrategy> clazz = PathExtensionContentNegotiationStrategy.class;
        PathExtensionContentNegotiationStrategy strategy = manager.getStrategy(clazz);
        return (strategy != null ? strategy : new PathExtensionContentNegotiationStrategy());
    }


    /**
     * Creates a new {@link HttpOutputMessage} from the given {@link NativeWebRequest}.
     *
     * @param webRequest the web request to create an output message from
     * @return the output message
     */
    protected ServletServerHttpResponse createOutputMessage(NativeWebRequest webRequest) {
        HttpServletResponse response = webRequest.getNativeResponse(HttpServletResponse.class);
        Assert.state(response != null, "No HttpServletResponse");
        return new ServletServerHttpResponse(response);
    }

    /**
     * Writes the given return value to the given web request. Delegates to
     * {@link #writeWithMessageConverters(Object, MethodParameter, ServletServerHttpRequest, ServletServerHttpResponse)}
     */
    protected <T> void writeWithMessageConverters(T value, MethodParameter returnType, NativeWebRequest webRequest)
            throws IOException, HttpMediaTypeNotAcceptableException, HttpMessageNotWritableException {

        ServletServerHttpRequest inputMessage = createInputMessage(webRequest);
        ServletServerHttpResponse outputMessage = createOutputMessage(webRequest);
        writeWithMessageConverters(value, returnType, inputMessage, outputMessage);
    }

    /**
     * Writes the given return type to the given output message.
     *
     * @param value         the value to write to the output message
     * @param returnType    the type of the value
     * @param inputMessage  the input messages. Used to inspect the {@code Accept} header.
     * @param outputMessage the output message to write to
     * @throws IOException                         thrown in case of I/O errors
     * @throws HttpMediaTypeNotAcceptableException thrown when the conditions indicated
     *                                             by the {@code Accept} header on the request cannot be met by the message converters
     */
    @SuppressWarnings({"rawtypes", "unchecked"})
    protected <T> void writeWithMessageConverters(@Nullable T value, MethodParameter returnType,
                                                  ServletServerHttpRequest inputMessage, ServletServerHttpResponse outputMessage)
            throws IOException, HttpMediaTypeNotAcceptableException, HttpMessageNotWritableException {

        Object outputValue;
        Class<?> valueType;
        Type declaredType;

        if (value instanceof CharSequence) {
            outputValue = value.toString();
            valueType = String.class;
            declaredType = String.class;
        } else {
            outputValue = value;
            valueType = getReturnValueType(outputValue, returnType);
            declaredType = getGenericType(returnType);
        }

        if (isResourceType(value, returnType)) {
            outputMessage.getHeaders().set(HttpHeaders.ACCEPT_RANGES, "bytes");
            if (value != null && inputMessage.getHeaders().getFirst(HttpHeaders.RANGE) != null) {
                Resource resource = (Resource) value;
                try {
                    List<HttpRange> httpRanges = inputMessage.getHeaders().getRange();
                    outputMessage.getServletResponse().setStatus(HttpStatus.PARTIAL_CONTENT.value());
                    outputValue = HttpRange.toResourceRegions(httpRanges, resource);
                    valueType = outputValue.getClass();
                    declaredType = RESOURCE_REGION_LIST_TYPE;
                } catch (IllegalArgumentException ex) {
                    outputMessage.getHeaders().set(HttpHeaders.CONTENT_RANGE, "bytes */" + resource.contentLength());
                    outputMessage.getServletResponse().setStatus(HttpStatus.REQUESTED_RANGE_NOT_SATISFIABLE.value());
                }
            }
        }


        List<MediaType> mediaTypesToUse;

        MediaType contentType = outputMessage.getHeaders().getContentType();
        if (contentType != null && contentType.isConcrete()) {
            mediaTypesToUse = Collections.singletonList(contentType);
        } else {
            HttpServletRequest request = inputMessage.getServletRequest();
            List<MediaType> requestedMediaTypes = getAcceptableMediaTypes(request);
            List<MediaType> producibleMediaTypes = getProducibleMediaTypes(request, valueType, declaredType);

            if (outputValue != null && producibleMediaTypes.isEmpty()) {
                throw new HttpMessageNotWritableException(
                        "No converter found for return value of type: " + valueType);
            }
            mediaTypesToUse = new ArrayList<>();
            for (MediaType requestedType : requestedMediaTypes) {
                for (MediaType producibleType : producibleMediaTypes) {
                    if (requestedType.isCompatibleWith(producibleType)) {
                        mediaTypesToUse.add(getMostSpecificMediaType(requestedType, producibleType));
                    }
                }
            }
            if (mediaTypesToUse.isEmpty()) {
                if (outputValue != null) {
                    throw new HttpMediaTypeNotAcceptableException(producibleMediaTypes);
                }
                return;
            }
            MediaType.sortBySpecificityAndQuality(mediaTypesToUse);
        }

        MediaType selectedMediaType = null;
        for (MediaType mediaType : mediaTypesToUse) {
            if (mediaType.isConcrete()) {
                selectedMediaType = mediaType;
                break;
            } else if (mediaType.equals(MediaType.ALL) || mediaType.equals(MEDIA_TYPE_APPLICATION)) {
                selectedMediaType = MediaType.APPLICATION_OCTET_STREAM;
                break;
            }
        }

        if (selectedMediaType != null) {
            selectedMediaType = selectedMediaType.removeQualityValue();
            for (HttpMessageConverter<?> converter : this.messageConverters) {
                GenericHttpMessageConverter genericConverter =
                        (converter instanceof GenericHttpMessageConverter ? (GenericHttpMessageConverter<?>) converter : null);
                if (genericConverter != null ?
                        ((GenericHttpMessageConverter) converter).canWrite(declaredType, valueType, selectedMediaType) :
                        converter.canWrite(valueType, selectedMediaType)) {
                    outputValue = (T) getAdvice().beforeBodyWrite(outputValue, returnType, selectedMediaType,
                            (Class<? extends HttpMessageConverter<?>>) converter.getClass(),
                            inputMessage, outputMessage);
                    if (outputValue != null) {
                        addContentDispositionHeader(inputMessage, outputMessage);
                        if (genericConverter != null) {
                            genericConverter.write(outputValue, declaredType, selectedMediaType, outputMessage);
                        } else {
                            ((HttpMessageConverter) converter).write(outputValue, selectedMediaType, outputMessage);
                        }
                        if (logger.isDebugEnabled()) {
                            logger.debug("Written [" + outputValue + "] as \"" + selectedMediaType +
                                    "\" using [" + converter + "]");
                        }
                    }
                    return;
                }
            }
        }

        if (outputValue != null) {
            throw new HttpMediaTypeNotAcceptableException(this.allSupportedMediaTypes);
        }
    }

    /**
     * Return the type of the value to be written to the response. Typically this is
     * a simple check via getClass on the value but if the value is null, then the
     * return type needs to be examined possibly including generic type determination
     * (e.g. {@code ResponseEntity<T>}).
     */
    protected Class<?> getReturnValueType(@Nullable Object value, MethodParameter returnType) {
        return (value != null ? value.getClass() : returnType.getParameterType());
    }

    /**
     * Return whether the returned value or the declared return type extend {@link Resource}
     */
    protected boolean isResourceType(@Nullable Object value, MethodParameter returnType) {
        return Resource.class.isAssignableFrom(value != null ? value.getClass() : returnType.getParameterType());
    }

    /**
     * Return the generic type of the {@code returnType} (or of the nested type
     * if it is an {@link HttpEntity}).
     */
    private Type getGenericType(MethodParameter returnType) {
        if (HttpEntity.class.isAssignableFrom(returnType.getParameterType())) {
            return ResolvableType.forType(returnType.getGenericParameterType()).getGeneric().getType();
        } else {
            return returnType.getGenericParameterType();
        }
    }

    /**
     * @see #getProducibleMediaTypes(HttpServletRequest, Class, Type)
     */
    @SuppressWarnings({"unchecked", "unused"})
    protected List<MediaType> getProducibleMediaTypes(HttpServletRequest request, Class<?> valueClass) {
        return getProducibleMediaTypes(request, valueClass, null);
    }

    /**
     * Returns the media types that can be produced:
     * <ul>
     * <li>The producible media types specified in the request mappings, or
     * <li>Media types of configured converters that can write the specific return value, or
     * <li>{@link MediaType#ALL}
     * </ul>
     *
     * @since 4.2
     */
    @SuppressWarnings("unchecked")
    protected List<MediaType> getProducibleMediaTypes(HttpServletRequest request, Class<?> valueClass,
                                                      @Nullable Type declaredType) {

        Set<MediaType> mediaTypes = (Set<MediaType>) request.getAttribute(HandlerMapping.PRODUCIBLE_MEDIA_TYPES_ATTRIBUTE);
        if (!CollectionUtils.isEmpty(mediaTypes)) {
            return new ArrayList<>(mediaTypes);
        } else if (!this.allSupportedMediaTypes.isEmpty()) {
            List<MediaType> result = new ArrayList<>();
            for (HttpMessageConverter<?> converter : this.messageConverters) {
                if (converter instanceof GenericHttpMessageConverter && declaredType != null) {
                    if (((GenericHttpMessageConverter<?>) converter).canWrite(declaredType, valueClass, null)) {
                        result.addAll(converter.getSupportedMediaTypes());
                    }
                } else if (converter.canWrite(valueClass, null)) {
                    result.addAll(converter.getSupportedMediaTypes());
                }
            }
            return result;
        } else {
            return Collections.singletonList(MediaType.ALL);
        }
    }

    private List<MediaType> getAcceptableMediaTypes(HttpServletRequest request)
            throws HttpMediaTypeNotAcceptableException {

        List<MediaType> types = this.contentNegotiationManager.resolveMediaTypes(new ServletWebRequest(request));
        return (types.isEmpty() ? Collections.singletonList(MediaType.ALL) : types);
    }

    /**
     * Return the more specific of the acceptable and the producible media types
     * with the q-value of the former.
     */
    private MediaType getMostSpecificMediaType(MediaType acceptType, MediaType produceType) {
        MediaType produceTypeToUse = produceType.copyQualityValue(acceptType);
        return (MediaType.SPECIFICITY_COMPARATOR.compare(acceptType, produceTypeToUse) <= 0 ? acceptType : produceTypeToUse);
    }

    /**
     * Check if the path has a file extension and whether the extension is
     * either {@link #WHITELISTED_EXTENSIONS whitelisted} or explicitly
     * {@link ContentNegotiationManager#getAllFileExtensions() registered}.
     * If not, and the status is in the 2xx range, a 'Content-Disposition'
     * header with a safe attachment file name ("f.txt") is added to prevent
     * RFD exploits.
     */
    private void addContentDispositionHeader(ServletServerHttpRequest request, ServletServerHttpResponse response) {
        HttpHeaders headers = response.getHeaders();
        if (headers.containsKey(HttpHeaders.CONTENT_DISPOSITION)) {
            return;
        }

        try {
            int status = response.getServletResponse().getStatus();
            if (status < 200 || status > 299) {
                return;
            }
        } catch (Throwable ex) {
            // ignore
        }

        HttpServletRequest servletRequest = request.getServletRequest();
        String requestUri = rawUrlPathHelper.getOriginatingRequestUri(servletRequest);

        int index = requestUri.lastIndexOf('/') + 1;
        String filename = requestUri.substring(index);
        String pathParams = "";

        index = filename.indexOf(';');
        if (index != -1) {
            pathParams = filename.substring(index);
            filename = filename.substring(0, index);
        }

        filename = decodingUrlPathHelper.decodeRequestString(servletRequest, filename);
        String ext = StringUtils.getFilenameExtension(filename);

        pathParams = decodingUrlPathHelper.decodeRequestString(servletRequest, pathParams);
        String extInPathParams = StringUtils.getFilenameExtension(pathParams);

        if (!safeExtension(servletRequest, ext) || !safeExtension(servletRequest, extInPathParams)) {
            headers.add(HttpHeaders.CONTENT_DISPOSITION, "inline;filename=f.txt");
        }
    }

    @SuppressWarnings("unchecked")
    private boolean safeExtension(HttpServletRequest request, @Nullable String extension) {
        if (!StringUtils.hasText(extension)) {
            return true;
        }
        extension = extension.toLowerCase(Locale.ENGLISH);
        if (this.safeExtensions.contains(extension)) {
            return true;
        }
        String pattern = (String) request.getAttribute(HandlerMapping.BEST_MATCHING_PATTERN_ATTRIBUTE);
        if (pattern != null && pattern.endsWith("." + extension)) {
            return true;
        }
        if (extension.equals("html")) {
            String name = HandlerMapping.PRODUCIBLE_MEDIA_TYPES_ATTRIBUTE;
            Set<MediaType> mediaTypes = (Set<MediaType>) request.getAttribute(name);
            if (!CollectionUtils.isEmpty(mediaTypes) && mediaTypes.contains(MediaType.TEXT_HTML)) {
                return true;
            }
        }
        return safeMediaTypesForExtension(new ServletWebRequest(request), extension);
    }

    private boolean safeMediaTypesForExtension(NativeWebRequest request, String extension) {
        List<MediaType> mediaTypes = null;
        try {
            mediaTypes = this.pathStrategy.resolveMediaTypeKey(request, extension);
        } catch (HttpMediaTypeNotAcceptableException ex) {
            // Ignore
        }
        if (CollectionUtils.isEmpty(mediaTypes)) {
            return false;
        }
        for (MediaType mediaType : mediaTypes) {
            if (!safeMediaType(mediaType)) {
                return false;
            }
        }
        return true;
    }

    private boolean safeMediaType(MediaType mediaType) {
        return (WHITELISTED_MEDIA_BASE_TYPES.contains(mediaType.getType()) ||
                mediaType.getSubtype().endsWith("+xml"));
    }

}
